Question

a youthful person run at 7km/h in a north- west direction across the derk of a ship in which is streaming due east at 40 km/h .ifind the velocity of the boy relative to the Sea
ii,And the velocity of the sea relative to the boy

Answer 1

i)

$$v=\sqrt{(7\cos 45)^2+(40-7\sin 45)^2}=35.4\frac{km}{h}\\ \theta=\arctan{\frac{7\cos 45}{(40-7\sin 45)}}=8.0\degree\text{ N of E}$$

ii)

$$v=35.4\frac{km}{h}\\ \theta=8.0\degree\text{ S of W}$$